2 | 17. df-traversal(the_graph;s1) 18. j:Vertices(the_graph). (inr(j) s1)  (inl(j) s1)  j-the_graph- > *i1 19. ( j:Vertices(the_graph).
(inr(j) [inr(i1) / s1])  (inl(j) [inr(i1) / s1])  j-the_graph- > *i1)

df-traversal(the_graph;s2 @ [inr(i1) / s1]) df-traversal(the_graph;[inl(i1) / (s2 @ [inr(i1)] @ s1)]) | 33 steps |